ISEE-3/ICE

The International Sun-Earth Explorer (ISEE) program consisted of 3 satellites-- ISEE-1 and ISEE-3 were the principal US contribution to the International Magnetospheric Study, and ISEE-2 which was built and managed by ESA. ISEE-1 and -2 were launched on 22 October 1977 into almost coincident orbits. The orbital period was 57 hours, and their separation in the orbit was controlled by manuvuering ISEE-2. ISEE-3 was launched on 12 August 1978. It was inserted into a "halo" orbit about the libration point some 240 Earth radii upstream between the Earth and Sun. ISEE-3 was renamed ICE (International Cometary Explorer) when, after completing its original mission in 1982, it was gravitationally manuvuered to intercept the comet P/Giacobini-Zinner. On September 11, 1985, the veteran NASA spacecraft flew through the tail of the comet.
An extended ICE mission was approved by NASA in 1991 for the continued investigation of coronal mass ejections, continued cosmic ray studies, and coordinated observations with Ulysses. It will return to the vicinity of the Earth-moon system in August 2014.

Source: http://heasarc.gsfc.nasa.gov/docs/heasarc/missions/isee3.html